We're going to stick our necks out here and assume you've almost all got a mobile. Many can't cope without it. Yet millions are overpaying. Either by letting contracts roll over and effectively paying for a phone you already own, being hounded into expensive upgrades, or just not searching for the best deals.

Most shouldn't pay more than £10/mth. The cheapest way to run a phone is usually to own it outright (if you can) & pair with a top Sim. Data and call charges have massively dropped in recent years - that's why we say the key benchmark cost for most users is £10/mth (see point 2).

Start by estimating what allowances you need. Specialist free online tools such as Billmonitor* will log in to your online phone account and analyse your bills to find your cheapest tariff. MobilePhoneChecker* covers more networks. See Mobile matchmaking.

2.

Check for the best Sim-only deals. They are increasingly popular due to their value and flexibility. You get a set amount of data, texts and calls for a fixed monthly price and they are usually cheapest.

- Best for low users: Get 1.5GB of data (4G), 250 mins and 5,000 texts for £5/mth on a 30-day rolling contract with Carphone-Warehouse-owned iD Mobile*, which uses the Three network.

- Best for medium users: We've blagged 5GB of data (4G), 1,500 mins and unltd texts for £10/mth with this 30-day rolling contract with BT-owned Plusnet Mobile*, for new and existing custs. It uses the EE network, and you've until next Tue to get it.

- Best for heavy users: Until Thu, this blagged 12mth contract from BT Mobile* gives a massive 20GB of data (4G), unltd mins and texts (on EE) for £16/mth if you've BT b'band, £21/mth if not. (To pay £16/mth click 'got BT b'band at home' in top right of page.)
You also get a £100 Amzn or iTunes vch - annoyingly, BT WON'T remind you so you must claim the voucher within 2wks-3mths of sign-up.

For a full round-up of top deals, incl out-of-bundle costs; plus higher/lower use and other network deals, see Sim-only top picks.

3.

New. Get £50 off the Samsung S8 or iPhone 7. These top-end handsets aren't MoneySaving... though if you'll get one anyway, do it as cheaply as possible. Discounts on newly launched handsets are rare, yet we've blagged £50 off the new Samsung S8 (released last Fri) AND the iPhone 7, from online retailer Unshackled.com*.

- £50 off code. Until Tue 9 May, use code MSE50 to take £50 off the upfront cost of either (when you click through, select 'outright'). This brings the Samsung S8* down to £639 and the 32GB iPhone 7* to £549, with next-day delivery included. (Unshackled says if you get the deal via a cashback site you won't get any cashback.)

- What if it runs out of stock? There's limited stock, particularly for the S8, so if it's right for you, go quick. Unshackled says it gets new deliveries every weekday and if it runs out you'll be invited to register and contacted within 24hrs of new stock arriving. The code will remain valid for a 'limited' time after.

- Will it be cheapest? Mobile prices change hourly, but these were the cheapest we could find from a UK-based retailer. You'll get a full UK manufacturer's warranty, so if something goes wrong you can take the handset to the nearest Samsung or Apple store (or authorised repair centre).

- But do you REALLY need a top-end smartphone? While many go wild for iPhones and Samsungs, there are plenty of low-cost models which search the web, play music, have cameras etc. See Cheap smartphone alternatives.

4.

Save more by getting certified pre-owned handsets - our code gets a further £40 off the iPhone 6s, 6s Plus, 6 or 6 Plus. 'Certified pre-owned' iPhones are the gold standard of refurbs - refurbished by Apple to a very high standard (often they've never been used), but for a lower price. If you're happy to go with an older model, even just from last year, you can save big.

- Get £40 off many iPhones in the 6 & 6s range: Until Tue 9 May, use code MSE40 at Unshackled.com to get £40 off its 'certified pre-owned' iPhones (when you click through, select 'outright').

Can't afford to buy the phone upfront? Spread the cost INTEREST-FREE. While it's usually the cheapest way to buy, many balk at having to pay £100s upfront. Yet there are other ways to spread the cost which are usually much cheaper than a contract...

- Buy it upfront on a 0% spending credit card: This is a free way to spread the cost - you can currently get up to 30 interest-free months (see our 0% card best buys). ALWAYS make minimum repayments and clear it before the 0% ends.

- Get a LOW interest rate with mobile financing: If you can't get approved for a 0% deal, specialist mobile finance providers loan you money for a handset at a cost - Unshackled is one, and our blagged codes work on its finance plans too. These usually beat most contracts, but ALWAYS do a comparison.

6.

Sometimes contracts CAN win. As a rule, you'll pay more with a contract. Occasionally though contract re-sellers (middlemen between you and the network) can beat buying upfront and pairing with a Sim. See full help in our 14 Mobile Contract tips.

7.

Going away? Roam free with a Three Sim. Using your phone abroad can be eye-wateringly expensive. Mercifully, from 15 Jun roaming fees in Europe will largely (though not entirely) disappear. Outside the EU it's a different story, with some providers charging up to £6/MB for data roaming.

Contract up? Switch or haggle NOW. Mobile contracts have high monthly costs, yet once you reach your 'minimum term' the payments often continue - so you're effectively paying for a phone you already own.

Diarise to call your network 30 days before and give notice, then move to a Sim-only tariff - by switching to another deal or haggling down your bill with your existing provider, as Suzanne did: "My £24/mth phone contract was about to run out. Saw a good deal in the weekly email so went to EE armed with this info - it agreed to give me 5GB and unltd mins & texts for £8/mth. Thank you."

Mid-contract? You're likely stuck... The only way to escape is to pay the remainder of the contract in full (or thereabouts). If your provider hikes prices mid-contract you MAY be able to escape penalty-free - though they're allowed to raise tariffs by inflation each year.

9.

Switching network's easy - and you can keep your number. Just request the PAC code from your current network to move your existing number over. The switch usually takes place the working day after you submit the PAC code to your new provider.

10.

You're credit-checked if getting a contract. If your credit history is poor, PAYG may be your only option. Bad credit means you may struggle to be approved for a phone or Sim-only contract. Pay-as-you-go deals aren't as cheap, but crucially you won't be credit-checked.

If you want to check your credit history, you can get your free credit report and credit score by joining our free MSE Credit Club.

11.

Get your phone unlocked for FREE. For a new Sim to work in an existing handset, it must be unlocked. Networks can no longer charge to unlock your phone if you're out of contract - and even if you're still in your minimum term, most choose not to. See Free mobile unlocking.

12.

Cover ALL the family's phones from £10/mth - but do you need insurance? Many don't - it's all about whether you're a loser. See our Mobile Insurance guide to help decide and find top picks from £6/mth per person, £10/mth for a family - which smash networks' charges.

Latest figures show a measly 1 in 70 current accounts were switched in the last year, yet we regularly hear your complaints. So stop bitching and start switching. Since 7-day switching launched in 2013 it's been easy, taking just 7 working days, and the new bank closes your old account and moves all payments. Now two giants have boosted their bribes to lure you in - both credit-check you & you must use their switching services to get the perks. Full options in Best Bank Accounts, in brief...

New. Free £125 M&S gift card + 5% regular saver + £5/mth for a year. M&S Bank* gives switchers a £125 M&S gift card, access to its 5% fixed regular savings account and a £100 0% overdraft. Plus for the first year, it'll add £5/mth to the card if you pay in at least £1,000/mth. You need to switch 2+ active direct debits for the initial gift card and keep them active for the £5/mth.

Boosted. Free £125 + No.1 rated service + 5% regular saver. Newbies applying via this First Direct* link get £125 (go direct & it remains at £100) and access to its 5% fixed regular saver. There's also a £250 0% overdraft, and 90% rated it as 'great' in our last poll. You must pay in £1,000/mth (or there's a £10/mth fee).

We've been swamped with successes since we launched Big Switch Event 7, our latest energy collective where firms bid to provide you cheap energy through a trusted intermediary (ie, us). Vicky told us: "Saved £800/yr. Thank you." And Gareth tweeted: "@Moneysaving Exp@MartinSLewis Just saved £368/yr in the big energy switch." Yet we've only 36,000 tariffs remaining and 8 days left to get 'em - so you need to act quick.

MSE super-cheap 1yr fix - £854/yr all-in based on typical use. Our winner's the Green Star Energy Rate Saver 12month Fixed MSE tariff (for dual fuel, single and Eco7). It costs a typical £884/yr for dual fuel, plus you get £30 MSE cashback (£15 single fuel), making it £854/yr all-in. It's available across Britain (sadly not NI), and the rate's locked for a year, though what you pay varies with use.

To get it, do a full market comparison (this link defaults to include cashback) and if you're eligible for the collective, it'll show in your results.

- Who is Green Star? It's a decent supplier that's taken part in our Big Switch Events before. It's been around since 2013, has nearly 200,000 customers and is owned by a large Canadian company. Plus, we've secured boosted customer service, so there's a special team just for this.

Be aware - if you switched 1yr ago it's now pricier. Unfortunately the cost of the cheapest deals has risen by 21% since last May, as wholesale costs have risen. And we can't beat the market. But this is one of the cheapest available now - it'll still save an average £280/yr versus standard rates you'd move to when your fix ends.

A new provider not yet on comparison may win on price. Newbie One Select has launched a tariff that on the surface undercuts our collective, though it's so new it hasn't yet provided the data for inclusion on most comparison sites. You can check it out yourself, yet we've no details of its customer service, capacity to cope if lots apply or its financial strength. We're telling you as we didn't want you to think we're hiding it.

1. Switching's easy. It's the same gas, same elec, same safety. Only service & price may change.
2. To get the lowest price, pay by monthly direct debit. Just ensure you give regular meter readings.
3. You CAN'T get Warm Home Discount with this tariff. So if you get it, this may not be for you.
4. If you're in credit and switch firm, you should get the excess back. If not, see get credit back.
5. Where we're paid to switch you we share roughly half in cashback. The rest covers our costs/profit.
6. This tariff is fixed. So the RATE (not cost, that depends on use) is locked in, with no hikes.
7. It charges £30/fuel early exit fees. Unless you leave it to move home.

Many are scared off investing in stock markets as it's complex. New 'robo-funds' aim to make it simpler - you answer a few questions, select your risk level and they choose (from a limited choice) where your money goes. Like all investing, be prepared to leave your money for a decent period (say 5yrs+) to ride market ups and downs. Be aware too that you could LOSE money.

Is robo-investing a good idea? Yes, it's a good idea - but that doesn't make it a good investment. For those prepared to do the research, picking your own shares and funds can mean lower fees and gives a much wider investment choice. Those with complex affairs can benefit by paying for an independent financial adviser too.

Now it should be noted that we at MSE don't usually cover investing. Our focus here is the cashback, which effectively gives a head start, as unless your investment falls by more than that you're quids in. Yet we're NOT suggesting this is the way to invest, just that if you're doing it anyway, be sure to bag the cashback.

Get £50 cashback on £500 Wealthify investment. Via this Wealthify* link, the first 500 new custs to open and fund a stocks & shares ISA (or ordinary investment plan) will get £50 cashback if they invest £500. The cashback'll be paid after 11mths as long as you invest an initial £500 lump sum, or £250 upfront & 10 subsequent monthly top-ups of £25 or more; and don't withdraw for a year. Total annual charges will be about 0.9% (sub-£5), assuming the final value stays the same.

Get £500 cashback on £5,000 Moneyfarm investment. The first 500 new customers to Moneyfarm who open and fund a stocks & shares ISA (or ordinary savings plan) via this Moneyfarm* link using code MSEcashback can earn £500 cashback. To get it, you must invest a min £5,000 lump sum or a min £2,500 upfront with 10 monthly top-ups of £250 or more; and don't withdraw for a year. If you invest that amount, total annual charges will be about 0.25% (£10ish), assuming no change in the final value.

Robo-investing need-to-knows:
- You can't pick your own funds. Your cash is invested in funds chosen by the robo-provider based on how risky you want to be.
- The bigger your investment, the less cashback will matter. If you invest more than the min needed to receive the cashback, you'll rely more on market movements to boost your returns in relation to the cashback.
- WARNING. Markets can sink as well as shoot up. As with any investments, your funds' value can go down as well as up, and while it's unlikely, you could lose all your money.

Should the state pension triple lock end? The state pension is set to rise in line with average wage growth, inflation or 2.5% - whichever's highest. But there's now an election debate over whether the 2.5% element should stay.

Keeping a pet is sometimes 'cheep'. For those with pets who voted in last week's poll, unsurprisingly horses were the most expensive to keep, costing an average of £2k to £5k a year, while fish were the cheapest at an average of less than £100 a year. See our full pet cost poll results.

Q: I have approx £35k in student loans that I've only just started paying back. My partner and I are saving for a first home and hope to be looking for one by the end of next year, but I've been told I could struggle to get a mortgage because of the loans - is this true? Sarah, via email.

MSE Sam Mc's A: Not necessarily. It's all about what you can afford. When deciding whether to grant you a mortgage, lenders will assess your financial commitments such as student loan payments, mobile phone bills, broadband costs etc to work out what spare cash you have each month to pay your mortgage.

If the combination of those repayments push you over the edge it may have an effect, but lenders are unlikely to decline you simply for having the student loan debt. For full help see our First-Time Buyers' Mortgage Guide.

That's it for this week but before we go, loyalty points can get you some serious bargains and our users have reported bagging everything from trips to America and Legoland to new cars, flights, rail passes and even a wedding ring. Have you ever grabbed a points-financed bargain? Let us know and see others' successes in our Facebook discussion: 'What's the best you've 'bought' with loyalty points?'

We think it's important you understand the strengths and limitations of this email and the site. We're a journalistic website, and aim to provide the best MoneySaving guides, tips, tools and techniques - but can't promise to be perfect, so do note you use the information at your own risk and we can't accept liability if things go wrong.

What you need to know

This info does not constitute financial advice, always do your own research on top to ensure it's right for your specific circumstances - and remember we focus on rates not service.

We don't as a general policy investigate the solvency of companies mentioned, how likely they are to go bust, but there is a risk any company can struggle and it's rarely made public until it's too late (see the Section 75 guide for protection tips).

We often link to other websites, but can't be responsible for their content.

Always remember anyone can post on the MSE forums, so it can be very different from our opinion.

More about MoneySavingExpert and Martin Lewis

What is MoneySavingExpert.com?Founded in February 2003, it's now the UK's biggest consumer help website with more than 12 million people getting this email and about 13 million using the site every month. In September 2012 it became part of the MoneySupermarket Group PLC. Its focus is simple: saving cash and fighting for financial justice on anything and everything. The site has over 80 full time staff, more than a third of whom are editorial - researching, analysing and writing to continually find ways to save money. More info: See About MSE.

Who is Martin Lewis?
Martin set up and is chairman of MSE. He's an ultra-focused money-saving journalist and consumer campaigner with his own ITV prime-time show The Martin Lewis Money Show and weekly slots on Radio 5 Live, This Morning and Good Morning Britain, among others. He's a columnist for publications including the Telegraph, Sunday Mirror and Woman magazine. More info: See Martin Lewis' biography.

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As we believe transparency is important, we're including the following 'un-affiliated' web-addresses for content too:

MoneySupermarket.com Financial Group Limited is authorised and regulated by the Financial Conduct Authority (FRN: 303190). The registered office address of both MoneySupermarket.com Group PLC and MoneySupermarket.com Financial Group Limited (registered in England No. 3157344) is MoneySupermarket House, St. David's Park, Ewloe, Chester, CH5 3UZ. MoneySavingExpert.com Limited is an appointed representative of MoneySupermarket.com Financial Group Limited.

How this site works

We think it's important you understand the strengths and limitations of the site. We're a journalistic website and aim to provide the best MoneySaving guides, tips, tools and techniques, but can't guarantee to be perfect, so do note you use the information at your own risk and we can't accept liability if things go wrong.

This info does not constitute financial advice, always do your own research on top to ensure it's right for your specific circumstances and remember we focus on rates not service.

Do note, while we always aim to give you accurate product info at the point of publication, unfortunately price and terms of products and deals can always be changed by the provider afterwards, so double check first.

We don't as a general policy investigate the solvency of companies mentioned (how likely they are to go bust), but there is a risk any company can struggle and it's rarely made public until it's too late (see the Section 75 guide for protection tips).

We often link to other websites, but we can't be responsible for their content.

Always remember anyone can post on the MSE forums, so it can be very different from our opinion.

MoneySavingExpert.com is part of the MoneySupermarket Group, but is entirely editorially independent. Its stance of putting consumers first is protected and enshrined in the legally-binding MSE Editorial Code.